Bioprospecting of Sphingobium yanoikuyae SS02 for Exopolysaccharide Production: Optimization, Characterization, and...

In the present study, an exopolysaccharide (EPS)-producing bacterial strain was isolated and identified as Sphingobium yanoikuyae SS02 using 16 S rRNA gene sequencing. Optimization of the culture medium through a one-factor-at-a-time (OFAT) approach enhanced EPS yield to 6.5 ± 0.2 g/L under mesophilic conditions. The purified EPS was structurally and functionally characterized using UV-Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Nuclear Magnetic Resonance (NMR), and Thermogravimetric Analysis (TGA). Spectroscopic analyses confirmed a glucose-rich heteropolysaccharide backbone with diverse functional groups, exhibiting moderate crystallinity and thermal stability, with major decomposition occurring between 150 °C and 330 °C. Biological evaluation revealed that the EPS possessed concentration-dependent antioxidant activity, with an IC50 of 0.635 mg/mL in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and 92.5% and 78.3% inhibition for ascorbic acid and EPS, respectively, in the phosphomolybdenum assay. The EPS also exhibited notable anti-inflammatory activity with 72.57% inhibition at 800 µg/ml, and broad-spectrum antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Bacillus subtilis, and Escherichia coli, with the highest sensitivity observed in S. aureus. These findings demonstrate the multifunctional bioactivity and biocompatibility of S. yanoikuyae SS02-derived EPS, suggesting its potential as a natural therapeutic agent for pharmaceutical and biomedical applications.